Both U.S. Pat. No. 4,776,514 and application Ser. No. 980,983, filed Nov. 24, 1992 and now U.S. Pat. No. 5,304,781, illustrate a two terminal line voltage thermostat in which one of the terminals is connected to, for example, a baseboard heater load and the other is connected to the other side of the line voltage. Then the other terminal of the heater load is connected to the opposite side of the line voltage. In the above patent and application there is described a transformer technique by which the control circuitry of the thermostat is powered from the line voltage during either on or off conditions of the heater load. In-two-terminal applications, sophisticated thermostats are available, for example, Honeywell Inc. has a model T498S, which uses a microcontroller, powered by battery only, to schedule and manage temperature control setback activity; the temperature sensing and control are performed mechanically with a bimetal plate and mechanical switch. Honeywell also has a model, T4798, which uses a microcontroller for setback activity as well as temperature sensing and control.